Ink jet printers are a well known and widely used form of printing. Ink is fed to an array of digitally controlled nozzles on a printhead. As the print head passes over the media, ink is ejected to produce an image on the media.
Printer performance depends on factors such as operating cost, print quality, operating speed and ease of use. The mass, frequency and velocity of individual ink drops ejected from the nozzles will affect these performance parameters.
Recently, the array of nozzles has been formed using micro electro mechanical systems (MEMS) technology, which have mechanical structures with sub-micron thicknesses. This allows the production of printheads that can rapidly eject ink droplets sized in the picolitre (×10−12 litre) range.
While the microscopic structures of these printheads can provide high speeds and good print quality at relatively low costs, their size makes the nozzles extremely fragile and vulnerable to damage from the slightest contact with fingers, dust or the media substrate. This can make the printheads impractical for many applications where a certain level of robustness is necessary. Furthermore, a damaged nozzle may fail to eject the ink being fed to it. As ink builds up and beads on the exterior of the nozzle, the ejection of ink from surrounding nozzles may be affected and/or the damaged nozzle will simply leak ink onto the substrate. Both situations are detrimental to print quality.
In other situations, a damaged nozzle may simply eject the ink droplets along a misdirected path. Obviously, this also detracts from print quality.